Adventures in LCR Phonos

What people are working on at the moment
simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Adventures in LCR Phonos

Post by simon » Mon Jul 02, 2018 10:20 pm

This is going to be a bit of a long running project I think.

I was inspired by hearing Shaman's (hello Nigel!) DIYHiFiSupply Cole LCR at Steve's t'other weekend, there was a "rightness" that stood out. Nick lent me his S&B 600R LCRs at Owston on Saturday, so there's no going back! :-)

Phonos, and LCR phonos especially, are finicky things so I reckon the place to start is the Cole, not least because I think it used the same S&B LCRs, I probably have most of the bits, the circuit's available, and I have an idea of what it should sound like.

http://www.store.diyhifisupply.com/cole ... q=node/827

Image

The Cole isn't produced anymore, but I did email Brian Cherry and DIYHiFiSupply to check a couple of details but didn't get a response. Nick's sensible advice is to keep it simple,and my first thoughts are to bin the crazy looking B+ PS. I've some Salas Simplistic Mosfet High Voltage Shunt (SSHV2) kits I've been wanting to use for quite a while so this looks like a decent place to start.

http://www.diyaudio.com/forums/power-su ... -regs.html

Don't hold your breathe for rapid progress!

Ant
Old Hand
Posts: 540
Joined: Mon Jul 31, 2017 6:45 pm
Location: Yorkshire

Re: Adventures in LCR Phonos

Post by Ant » Tue Jul 03, 2018 2:14 pm

That Cole certainly made an impression eh simon!

User avatar
Nick
Site Admin
Posts: 11227
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

Re: Adventures in LCR Phonos

Post by Nick » Tue Jul 03, 2018 3:36 pm

I have my doubts about the second ecc88 in grid leak mode, but it will do no harm to start there.
Resistance isn't futile it's V / I.

User avatar
Nick
Site Admin
Posts: 11227
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

Re: Adventures in LCR Phonos

Post by Nick » Tue Jul 03, 2018 3:38 pm

I would also check if thats using the S&B riaa, it assumes there is no path to ground from the input and the caps in there are good for 65v.
Resistance isn't futile it's V / I.

Andrew
Eternally single
Posts: 4054
Joined: Thu May 24, 2007 2:18 pm

Re: Adventures in LCR Phonos

Post by Andrew » Tue Jul 03, 2018 4:12 pm

I would ditch the grid leak bias, that big resistor is a potential source of hum noise, and as the 88 ages it may runaway, especially if you replace the 88 with something with more GM, like D3A.

By all means try it as is, but be prepared to chase hum. This is one of those times when a bigger cap and a smaller resistor isn't a bad thing.

Andrew
Analogue, the lost world that lies between 0 and 1.

simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Re: Adventures in LCR Phonos

Post by simon » Tue Jul 03, 2018 6:40 pm

Ant wrote:
Tue Jul 03, 2018 2:14 pm
That Cole certainly made an impression eh simon!
Yeah, it sure did :-)

izzy wizzy
Old Hand
Posts: 459
Joined: Fri Nov 02, 2007 7:02 pm
Location: Folkestone
Contact:

Re: Adventures in LCR Phonos

Post by izzy wizzy » Tue Jul 03, 2018 6:41 pm

It looks like Thorsten Loesch designed the Cole or had a hand in it.

He used the S&B LCR in his own http://www.izzy-wizzy.com/audio/phono/T ... nal6xz.gif

He started in another direction earlier in its design http://www.izzy-wizzy.com/audio/phono/T ... 0026xz.gif

These cover both choices: drive with 600R, load lightlty OR drive from high Z, load with 600R

He liked grid leak bias. In the Cole, the 2nd stage has a cathode resistor which might help with runaway.

cheers,

Stephen

simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Re: Adventures in LCR Phonos

Post by simon » Tue Jul 03, 2018 6:43 pm

Nick wrote:
Tue Jul 03, 2018 3:36 pm
I have my doubts about the second ecc88 in grid leak mode, but it will do no harm to start there.
I've looked at the curves for the ECC88 and I struggled to get my head round the likely OPs. Think I might have said on Saturday? With just 65V on both anodes the different cathode resistors don't make much sense from a current POV.

simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Re: Adventures in LCR Phonos

Post by simon » Tue Jul 03, 2018 6:51 pm

Nick wrote:
Tue Jul 03, 2018 3:38 pm
I would also check if thats using the S&B riaa, it assumes there is no path to ground from the input and the caps in there are good for 65v.
According to the BOM on the link above they were S&B 600R units.

Can you explain a bit more what you mean by no path to ground from the input?

simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Re: Adventures in LCR Phonos

Post by simon » Tue Jul 03, 2018 7:01 pm

Andrew wrote:
Tue Jul 03, 2018 4:12 pm
I would ditch the grid leak bias, that big resistor is a potential source of hum noise, and as the 88 ages it may runaway, especially if you replace the 88 with something with more GM, like D3A.

By all means try it as is, but be prepared to chase hum. This is one of those times when a bigger cap and a smaller resistor isn't a bad thing.

Andrew
Good points well made.

I was having a look around Dave Slagle's forum earlier and found a thread that you Nick Mark and James posted on. I've only read the start of it but there were interesting discussions about pentodes and Aikidos. More reading to do.

Come on England!

User avatar
IslandPink
Thermionic Monk Status
Posts: 5985
Joined: Tue May 29, 2007 7:01 pm
Location: Denbigh, N.Wales

Re: Adventures in LCR Phonos

Post by IslandPink » Tue Jul 03, 2018 7:25 pm

Oh dear, I wonder what I posted on that ... !
Thanks for reminding me about that football match. I was up having a bath and had forgotten.
White flags of winter chimneys waving truce against the moon ( Mitchell )

User avatar
Nick
Site Admin
Posts: 11227
Joined: Sun May 06, 2007 10:20 am
Location: West Yorkshire

Re: Adventures in LCR Phonos

Post by Nick » Tue Jul 03, 2018 8:36 pm

simon wrote:
Tue Jul 03, 2018 6:51 pm
Can you explain a bit more what you mean by no path to ground from the input?
If you look at he circuit of the tango LCR, there is a resistive path from the input to the ground point. If you put 65v (as that circuit does) with no blocking cap then current will flow. May be ok, may not, can't say. You can check with a multimeter between the input and ground to see what the resistance is.
Resistance isn't futile it's V / I.

izzy wizzy
Old Hand
Posts: 459
Joined: Fri Nov 02, 2007 7:02 pm
Location: Folkestone
Contact:

Re: Adventures in LCR Phonos

Post by izzy wizzy » Tue Jul 03, 2018 9:04 pm

LCR modules come in 3 varieties. Some with a path to ground from theinput and some not
Attachments
induct7.gif

simon
Social outcast
Posts: 3935
Joined: Thu May 24, 2007 11:22 am
Location: People's Republic of South Yorkshire

Re: Adventures in LCR Phonos

Post by simon » Tue Jul 03, 2018 10:43 pm

Thanks Stephen, the last attachment was particularly helpful. And as far as I know Thorsten designed the Cole.

RhythMick
User
Posts: 141
Joined: Fri Jun 23, 2017 12:24 pm

Re: Adventures in LCR Phonos

Post by RhythMick » Wed Jul 04, 2018 7:44 am

I have an all-valve balanced LCR phono stage built by a friend. I'll bring it along to a meet some time.

EDIT - I may have missed the point of this thread. I'll get me coat.
Last edited by RhythMick on Wed Jul 04, 2018 8:52 am, edited 1 time in total.

Post Reply

Who is online

Users browsing this forum: No registered users and 3 guests